1. Field of the Invention
This invention relates to dispensers, and specifically to a flexible sheet material dispenser and a mechanism adapted to be used therein for perforating a web of flexible sheet material.
2. Description of the Prior Art
Dispensers for flexible sheet material, such as paper toweling have long been known which include mechanisms for perforating or severing a web of such material to divide the web into individual sheets. Representative of such dispensers are those disclosed in Hamilton et al. U.S. Pat. No. 1,133,640; Schroeder U.S. Pat. No. 1,449,062; Shelley U.S. Pat. No. 1,543,299; Walsh et al. U.S. Pat. No. 2,278,029; and Agamaite U.S. Pat. No. 2,560,061. The perforating or severing mechanisms used in these dispensers generally include a rotatably mounted knife and a cooperating rotatably mounted roller having a slot therein for receiving the radially outward portion of the knife as the knife rotates past the roller. The web of flexible sheet material is passed between the roller and the knife to be perforated or severed when the radially outward knife portion enters the slot in the roller.
Such mechanisms are satisfactory for perforating or severing relatively unstretchable flexible sheet materials, such as uncreped paper toweling. However, with the increased use of relatively stretchable flexible sheet materials, such as embossed and creped paper toweling, the prior art perforating and severing mechanisms have provided unsatisfactory because the web of sheet material tends to stretch about the cutting edge of the knife instead of being perforated or severed thereby. This problem results principally from the orientation of the cutting edge during the entrance of the radially outward knife portion into the slot; the cutting edge being oriented nonparallel to the direction in which the radially outward knife portion moves with respect to the web, causing the edge to slide along the web. Although precision rotary shears are known which could be employed for obviating this problem, for example, the rotary shears shown in Kalko U.S. Pat. No. 1,989,012, such shears are much too expensive to be used in flexible sheet material dispensers designed for installation in both commercial and private washrooms and kitchens.